System for charging a series of connected batteries

ABSTRACT

An apparatus is provided for charging a first storage battery and a second storage battery electrically connected together in series includes a first Kelvin connection, a second Kelvin connection and a third Kelvin connection coupled to the storage batteries. At least two of the Kelvin connections are configured to charge at least one of the first and second batteries. A charging source configured to selectively couple a charge signal to a storage battery through the Kelvin connections. A switching device selectively couples the charging source and measurement circuitry to at least two of the first, second and third Kelvin connections. A microprocessor selectively controls the switching device, charges the batteries, and measures a parameter of the batteries as a function of the charging signal applied to the batteries.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based on and claims the benefit of U.S.provisional patent application Ser. No. 62/930,781, filed Nov. 5, 2019,the content of which is hereby incorporated by reference in itsentirety.

BACKGROUND

Many trucking applications utilize two 12 volt batteries in series topower a 24 volt electrical system. When such a series of batteries arereplaced, charged, and maintained, it is well known in the art that thebatteries should be in as close of a state of charge and state of healthas possible. Otherwise, the system will rapidly degrade.

Conventional techniques for maintaining the 12 volt batteries of aseries in a close state of charge include the use of specialty 24 voltseries chargers. However, such chargers cannot prevent the occurrence ofan imbalance between the batteries.

Other techniques involve manually charging each of the batteriesindividually. However, this requires intervention and interpretation bya skilled technician to ensure that the batteries are properly balanced.Additionally, this method is very time consuming for the technician dueto the required swapping of charge leads, etc.

Various types of battery testers and charging equipment are known in theart. Examples of various battery testers, chargers and monitors areforth in: U.S. Pat. No. 3,873,911, issued Mar. 25, 1975, to Champlin;U.S. Pat. No. 3,909,708, issued Sep. 30, 1975, to Champlin; U.S. Pat.No. 4,816,768, issued Mar. 28, 1989, to Champlin; U.S. Pat. No.4,825,170, issued Apr. 25, 1989, to Champlin; U.S. Pat. No. 4,881,038,issued Nov. 14, 1989, to Champlin; U.S. Pat. No. 4,912,416, issued Mar.27, 1990, to Champlin; U.S. Pat. No. 5,140,269, issued Aug. 18, 1992, toChamplin; U.S. Pat. No. 5,343,380, issued Aug. 30, 1994; U.S. Pat. No.5,572,136, issued Nov. 5, 1996; U.S. Pat. No. 5,574,355, issued Nov. 12,1996; U.S. Pat. No. 5,583,416, issued Dec. 10, 1996; U.S. Pat. No.5,585,728, issued Dec. 17, 1996; U.S. Pat. No. 5,589,757, issued Dec.31, 1996; U.S. Pat. No. 5,592,093, issued Jan. 7, 1997; U.S. Pat. No.5,598,098, issued Jan. 28, 1997; U.S. Pat. No. 5,656,920, issued Aug.12, 1997; U.S. Pat. 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SUMMARY

An apparatus is provided for charging a first storage battery and asecond storage battery electrically connected together in seriesincludes a first Kelvin connection, a second Kelvin connection and athird Kelvin connection coupled to the storage batteries. At least twoof the Kelvin connections are configured to charge at least one of thefirst and second batteries. A charging source configured to selectivelycouple a charge signal to a storage battery through the Kelvinconnections. A switching device selectively couples the charging sourceand measurement circuitry to at least two of the first, second and thirdKelvin connections. A microprocessor selectively controls the switchingdevice, charges the batteries, and measures a parameter of the batteriesas a function of the charging signal applied to the batteries.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of a charging system or chargingseries connected storage batteries in accordance with one exampleembodiment of the present invention.

FIG. 2 is a simplified block diagram of another example embodiment ofthe charging system of FIG. 1 using Kelvin connections for coupling tothe storage batteries.

FIG. 3 is a schematic diagram showing a switch configured for couplingto a storage battery.

FIG. 4 is a simplified diagram showing operation of the switch of FIG.3.

FIG. 5 is a side perspective view showing one example configuration ofthe switch of FIGS. 3 and 4.

FIG. 6 is a schematic diagram showing a charging system in accordancewith a more detailed embodiment.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1 is a schematic diagram of an exemplary system 100 for performingbalanced charging of batteries 102 that are connected in series, such asbatteries 102A and 102B, in accordance with embodiments of the presentdisclosure. The batteries 102 may be 12 volt batteries that are pairedin series to supply 24 volts to an electrical load 104, such as anelectrical system of a truck or other load, for example.

The system 100 allows the series connected batteries 102 to be chargedwithout having to remove the batteries 102 and without having tomanually adjust battery connections. In some embodiments, the system 100includes a switching device 106 that selectively connects a chargingdevice 108, such as a conventional 12 volt battery charger or a fullycapable 12 volt diagnostic charger, to each of the batteries 102 forcharging, such as while the batteries remain connected to each other andthe load 104. Thus, while the charging device 108 may be configured toperform a charging algorithm, which may include conventional batterytests, on a single battery 102, the switching device 106 facilitatesselective connection of the charging device 108 to one of a plurality ofthe batteries 102 at a time, thereby allowing the charging device 108 toperform the charging algorithm on each of the batteries 102. In someembodiments, the switching device 106 automatically switches thecharging device 108 to the batteries without technician interventionfollowing the initial setup of the system 100.

The switching device 106 includes a switching mechanism 110 and a motordrive 112. The motor drive 112 is configured to actuate the switchingmechanism 110 to selectively mechanically link connections 114 (e.g.,inputs and/or outputs) of the charging device 108 to connections 116(e.g., inputs and/or outputs) of one of the batteries 108, such as inresponse to a control signal 118. For example, the control signal 118may initially direct the motor drive 112 to connect the connections 114of the charging device 108 to the connections 116A of the battery 102A,and the charging device 108 may perform a charging/testing algorithm onthe device 102A, during which the battery 102A is charged to a desiredlevel. The control signal 118 may then direct the motor drive 112 toconnect the connections 114 of the charging device 108 to theconnections 116B of the battery 102B, and the charging device 108 mayperform a charging/testing algorithm on the device 102B, during whichthe battery 102B is charged to a desired level. As mentioned above, thisprocess of generating the control signal 118 and performingcharging/testing routines on the batteries 102A and 102B may occurwithout technician intervention.

In some embodiments, the control signal 118 is generated by a controllerof the system 100, such as a controller of the charging device 108 or aseparate controller of the switching device 106, in accordance with acharging/testing algorithm. Such a controller may comprise one or moreprocessors configured to control the components of the switching device106 to generate the control signal 118 and perform method steps andfunctions described herein, in response to the execution of programinstructions stored in non-transitory computer readable media or memory.

The connections 114 of the charging device 108 and the connections 116of the batteries 102 may take on any suitable form, and may includeconventional connections. For example, the connections 114 of thecharging device 108 may include a positive charging terminal 114A, anegative charging terminal 114B, and an output 114C for the controlsignal 118, and the connections 116 of each battery 102 may include apositive battery terminal, such as positive battery terminals 116A-1 and116B-1, and a negative battery terminal, such as negative batteryterminals 116A-2 and 116B-2, as indicated in FIG. 1. In operation, thecontrol signal 118 may direct the motor drive 112 to actuate theswitching mechanism 110 to a first state, in which the positive chargingterminal 114A is connected to the positive battery terminal 116A-1, andthe negative charging terminal 114B is connected to the negative batteryterminal 116A-2, as indicated by the solid lines in FIG. 1. The controlsignal 118, such as after a charging/testing algorithm has beenperformed on the battery 102A by the charging device 108, may direct themotor drive 112 to actuate the switching mechanism to a second state, inwhich the positive charging terminal 114A is connected to the positivebattery terminal 116B-1, and the negative charging terminal 114B isconnected to the negative battery terminal 116B-2, as indicated by thesolid lines in FIG. 1. When the switching mechanism 110 is in thissecond state, the charging device 108 may perform a charging/testingalgorithm on the battery 102B.

In some embodiments, each of the connections 116 of the batteries 102includes a Kelvin connection 120 connected to the positive terminal anda Kelvin connection 122 connected to the negative terminal, as shown inthe schematic diagram of FIG. 2. Each Kelvin connection 120 and 122includes a sense connection and a current connection, in accordance withconventional Kelvin connections. Thus, the battery 102A includes aKelvin connection 120A having a sense connection 120As and a currentconnection 120Ac, and a Kelvin connection 122A having a sense connection122As and a current connection 122Ac Likewise, the battery 102B includesa Kelvin connection 120B having a sense connection 120Bs and a currentconnection 120Bc, and a Kelvin connection 122B having a sense connection122Bs and a current connection 122Bc.

The charging device 108 may include connections 114-1 s, 114-1 c, 114-2s and 114-2 c that are configured to connect the corresponding Kelvinconnections 120 and 122 through the switching mechanism 110, asindicated in FIG. 2. This allows the charging device 108 to performconventional complex charging/testing algorithms on the batteries 102Aand 102B, without technician intervention. Specifically, the connection114-1 s is configured to connect to the connections 120As or 120Bs, theconnection 114-1 c is configured to connect to the connections 120Ac or120Bc, the connection 114-2 s is configured to connect to theconnections 122As or 122Bs, and the connection 114-2 c is configured toconnect to the connections 122Ac or 122Bc, depending on the state of theswitch mechanism 110. When the switching mechanism 110 is directed to afirst state by the motor drive 112 in response to the control signal118, the connections 114-1 s and 114-1 c are connected to theconnections 120As and 120Ac, and the connections 114-2 s and 114-2 c areconnected to the connections 122As and 122Ac, respectively, as indicatedby the solid arrows. When the switching mechanism 110 is directed to asecond state by the motor drive 112 in response to the control signal118, the connections 114-1 s and 114-1 c are connected to theconnections 120Bs and 120Bc, and the connections 114-2 s and 114-2 c areconnected to the connections 122Bs and 122Bc, respectively.

The motor drive 112 may take on any suitable form. FIG. 3 includessimplified circuit diagrams illustrating an exemplary motor drive 112,in accordance with embodiments of the present disclosure. In someembodiments, the motor drive 112 includes a motor 130, such as a gearmotor, that drives the actuation of the switching mechanism 110 betweenvarious states, such as the exemplary first and second states describedabove, to selectively connect the connections 114 of the charging device108 to the connections 116 of the batteries 102.

The motor 130 may be driven using the circuit shown in FIG. 3, oranother suitable circuit. In one embodiment, the motor drive 112includes a double pole double through (DPDT) relay K1 that operates toreverse the polarity going to the motor 130, limit switches 132A and132B, diodes 134A and 134B, and a power supply 136. The relay K1 may bepowered by a power source 138 that is selectively connected to the relayK1 using a switch SW1. When the switch SW1 is open (shown), the currenttravels in one direction through the motor 130 and drives the switchingmechanism to the first state, and when the switch SW1 is closed, thecurrent travels through the motor 130 in the opposite direction anddrives the switching mechanism to the second state.

The switching mechanism 110 may include multiple switches thatfacilitate the selective coupling of the connections 114 to theconnections 116. FIG. 4 is a simplified diagram of an exemplary switch140 of the switching mechanism 110, which is generally represented asone of the arrows in FIGS. 1 and 2. In some embodiments, the switch 140includes connectors 142, such as connectors 142A-D, each of which may beconfigured to connect to a connection 114 of the charging device 108 ora connection 116 of the batteries 102. In some embodiments, a pair ofthe connectors 142, such as connectors 142A and 142B, may beelectrically connected through a suitable jumper 143, as shown in FIG.4, which allows the connectors 142A and 142B to be connected to the sameconnector 114 or 116.

For example, the connectors 142A and 142B may each be connected to theconnector 114A (FIG. 1) of the charging device 108 through the jumper143, the connector 142C may be connected to the connector 116A-1 of thebattery 102A, and the connector 142D may be connected to the connector116B-1 of the battery 102B, for example. Other switches 140 may beconnected in a similar manner to provide the desired couplings betweenthe connections 114 of the charging device 108 and the connections 116of the batteries 102.

The switch 140 may also include a shaft 144 that is driven by the motor130 to rotate about an axis 146 in a clockwise or counterclockwisemanner. In some embodiments, the direction of rotation that the shaft144 is driven by the motor 130 is determined by the flow of currentthrough the motor 130, which may be set by the relay K1 (FIG. 3), forexample.

Conductors 148, which extend radially from the shaft 144, are eachconfigured to engage one of the connectors 142 when the switch 140 isactuated to the first or second position. For example, when in a firststate or position, the conductor 148A is connected to the connector 142Aand the conductor 148B is connected to the connector 142D, as indicatedby the solid lines in FIG. 4. Thus, continuing with the example providedabove, the switch 140 would electrically connect the connection 114A tothe connection 116B-1 of the battery 102B. When the switch 140 isactuated to a second state or position (dashed lines), the connector148A is connected to the connector 142B and the conductor 148B isconnected to the connector 142C. Thus, continuing again with the currentexample, the switch 140 would electrically connect the connection 114Ato the connection 116A-1 of the battery 102A. Thus, using multipleswitches 140, the drive motor 112 may actuate the switches 140 toselectively couple the connections 114 to the connections 116 of thebatteries 102.

FIG. 5 is an isometric view of an exemplary switch assembly 150 thatincludes multiple switches 140, such as switches 140-1 and 140-2. Theswitch 140-1 includes connectors 142A-1, 142B-1, 142C-1 and 142D-1, andconductors 148A-1 and 148B-1. The connectors 142A-1 and 142B-1 arejoined together by a jumper 143-1. Similarly, the switch 140-2 includesconnectors 142A-2, 142B-2, 142C-2 and 142D-2, and conductors 148A-2 and148B-2. The connectors 142A-2 and 142B-2 are joined together by a jumper143-2. The switch assembly 150 is shown as being actuated to the secondstate or position, in which the conductors 148A-1 and 148B-1 of theswitch 140-1 are respectively coupled to the connectors 142B-1 and142C-1, and the conductors 148A-2 and 148B-2 of the switch 140-2 arerespectively coupled to the connectors 142B-2 and 142C-2. The switchassembly may be actuated to the first state or position using the motordrive 112, in which the conductors 148A-1 and 148B-1 of the switch 140-1are respectively coupled to the connectors 142A-1 and 142D-1, and theconductors 148A-2 and 148B-2 of the switch 140-2 are respectivelycoupled to the connectors 142A-2 and 142D-2.

The present invention provides an apparatus for charging a battery whichis also capable of monitoring the condition of the battery. Suchmonitoring can be used to provide information to an operator, or toprovide feedback to control the charging. The invention can use thecharging current and voltage themselves to advantageously determinebattery condition. Thus, a battery charger in accordance with thepresent invention is capable of determining the status of the battery,making advanced decisions about charging the battery and selecting aparticular charging profile used in such charging.

FIG. 6 is a simplified block diagram of a battery charging system 100 inaccordance with the present invention coupled to storage batteries102A,B which are typically lead-acid storage batteries of the type usedin automotive vehicles or standby electrical systems. Switching devices108 operates as discussed above under the control of a microprocessor234. System 100 includes battery charger circuitry and test circuitry214. Battery charge circuitry 212 generally includes AC source 216,transformer 218 and rectifier 220. System 100 couples to batteries102A,B through electrical connection 116 which couples to the positiveand the negative terminals of the batteries. In one preferredembodiment, a four point (or Kelvin) connection technique is used inwhich battery charge circuitry 212 couples to the batteries throughdevice 106 and battery testing circuitry 214 couples to batteriesthrough device 106.

Battery testing circuitry 214 includes voltage measurement circuitry 230and current measurement circuitry 232 which provide outputs tomicroprocessor 234. Microprocessor 234 also couples to a system clock236 and memory 238 which is used to store information and programminginstructions. In the embodiment of the invention shown in FIG. 6,microprocessor 234 also couples to user output circuitry 240 and userinput circuitry 242.

Voltage measurement circuitry 234 includes capacitors 250 which coupleanalog to digital converter 252 to batteries 102A,B. Any type ofcoupling mechanism may be used for element 250 and capacitors are merelyshown as one preferred embodiment. Further, the device may also coupleto DC signals. Current measurement circuitry 232 includes a shuntresistor (R), 260 and coupling capacitors 262. Shunt resistor 260 iscoupled in series with battery charging circuitry 212. Other currentmeasurement techniques are within the scope of the invention includingHall-Effect sensors, magnetic or inductive coupling, etc. An analog todigital converter 264 is connected across shunt resistor 260 bycapacitor 262 such that the voltage provided to analog to digitalconverter 264 is proportional to a current I flowing through batteries102A,B due to charging circuitry 212. Analog to digital converter 264provides a digitized output representative of this current tomicroprocessor 234.

During operation, AC source 216 is coupled to batteries 102A,B throughtransformer 218 and rectifier 220. Rectifier 220 provides half wayrectification such that current I has a non-zero DC value. Of course,full wave rectification or other AC sources may also be used. Analog todigital converter 264 provides a digitized output to microprocessor 234which is representative of current I flowing through batteries 102A,B.Similarly, analog to digital converter 252 provides a digitized outputrepresentative of the voltage across the positive and negative terminalsof batteries 102A,B. Analog to digital converters 252 and 264 arecapacitively coupled to batteries 102A,B that they measure the ACcomponents of the charging signal.

Microprocessor 234 determines the conductance of batteries 102A,B basedupon the digitized current and voltage information provided by analog todigital converters 264 and 252, respectively. Microprocessor 234 countsthe conductance of batteries 102A,B as follows:

Conductance=G=I/V,   Eq. 1

where I is the charging current and V is the charging voltage acrossbatteries 102A,B. Note that in one preferred embodiment the Kelvinconnections allow more accurate voltage determination because theseconnections do not carry substantial current to cause a resultant dropin the voltage measured.

In accordance with the present invention, the battery conductance isused to monitor charging of batteries 102A,B. Specifically, as a batteryis charged the conductance of the battery rises. This rise inconductance can be monitored in microprocessor 234 to determine when thebattery has been fully charged. For example, if the rate of the rise inconductance slowly decreases, such that the conductance reaches asubstantially constant value, microprocessor 234 determines thatbatteries 102A,B is fully charged and disconnect charging circuitry 212using switch 270. Further, in one aspect of the present invention,microprocessor 234 responsively controls the rate of charge by adjustingAC source 16 to reduce the likelihood that batteries 102A,B is damagedby significant overcharge.

Furthermore, microprocessor 234 can calculate cold cranking amps (CCA)of batteries 102A,B using the formula:

CCA−K·G   Eq. 2

where K is constant which may be selected for a specific battery and Gis given in Equation 1.

One aspect of the invention includes storing information inmicroprocessor 234 or memory 238 which relates to batteries 102A,B. Forexample, this information could be the battery's nominal CCA rating asinput through input 242 by an operator. Further, the make and model ofthe battery may be input by an operator through input 242 andinformation related to that specific battery type recovered from memory238. In general, the rating of the battery may be input in the form ofCCA, amp hours, RC, JIS number, stock number, battery construction orchemistry, etc. For example, if a nominal or reference conductance(G_(REFERENCE)) is stored in memory, a relative conductancedetermination can be made by microprocessor 234 using the equation:

Relative Conductance (%)=G _(measured) /G _(reference)×100,   Eq. 2

where G_(measured) is the battery conductance in accordance withEquation 1. Generally, this reference conductance is determined basedupon type and characteristics of batteries 102A,B. This technique isdescribed in U.S. Pat. No. 5,140,269, entitled ELECTRONIC TESTER FORASSESSING BATTERY/CELL CAPACITY, issued Aug. 18, 1992 to Champlin. Thismay be converted into a display for output on output 240 such that anoperator may monitor the charging of batteries 102A,B. For example,output 240 can be one in which a bar graph is provided with indicationsfor “empty” and “full.” This may be implemented through an LED display,for example. Other examples of desirable outputs include outputs whichappear as a gauge or other visual indication of the battery condition.Other types of outputs include outputs indicating the recovery of amphours, state of charge, reserve capacity, time to full charge or runtime remaining. This may be shown in percentages, numerically,graphically, etc.

Additional embodiments of the present disclosure are directed to methodsof performing charging and/or testing algorithms on individual batteriesthat are connected in series using the switching device 106 and thecharging device 108. In some embodiments, the method involvesselectively connecting connections 114 of the charging device tocorresponding connections 116 of one of the batteries 102 using aswitching mechanism 110 of a switching device 106, in accordance withone or more embodiments described herein. A charging and/or testingalgorithm is then performed on the battery using the charging device108. Next, the switching mechanism 110 is actuated by a drive motor 112in response to a control signal 118 to a state in which the connections114 of the charging device 108 are coupled to the connections 116 of adifferent battery in the series. A charging and/or testing algorithm isthen performed on the battery using the charging device 108.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. The various voltages and currents measuredherein are set forth as alternating signals and their measurements maybe through RMS values, peak-to-peak measurements, etc. However, othertechniques may be employed and DC signals may also be monitored. In atypical battery charger, the AC component of the charging signal isrelated to the line frequency and thus, in the United States, istypically 60 Hz or 120 Hz. However, other frequencies may also beemployed. Further, the charge signal may be a stepped DC signal and thevoltage and current measurement circuitry responsive to step DC signals.In general, the invention determines battery and/or charging conditionsbased upon a ratio of charging voltage and charging current. As usedherein and as will be recognized by those skilled in the art, the term“microprocessor” refers to any type of digital circuitry which operatesin accordance with stored logic. An example charging system is shown anddescribed in U.S. Pat. No. 6,313,608, which is incorporated herein byreference in its entirety. In one configuration, only three connectionsare used for coupling to two series connected storage batteries. Two ofthe connections electrically connect to the outer most positive andnegative battery terminals of the series batteries and a thirdconnection is configured to couple to one of the middle positive ornegative terminals of the series connected storage batteries. In such aconfiguration, the electrical connection between the two seriesconnected storage batteries may introduce some error in measurements dueto the electrical characteristics such as resistance of the electricalconnector. In another example configuration, if initial testing showsthat the two batteries are relatively well balanced, a single chargingsignal can be applied simultaneously through both of two seriesconnected storage batteries. In such a configuration, the condition ofthe two series connected storage batteries can still be monitored usinga proper configuration of the switching device. Although only twostorage batteries are discussed herein, any number of series connected(or series-parallel connected) storage batteries may be tested using thetechniques discussed herein and through the appropriate configuration ofthe switching device. In another example configuration, two switchingdevices are employed. One switching device can be used to control thecurrent connection to the storage batteries through the Kelvinconnectors and a second switching device can be used to control thevoltage sense connections to the batteries through the Kelvinconnections. In such a configuration, if signal levels are sufficientlylow, the second switching device can be a semiconductor device and doesnecessarily require the physical switch illustrated in FIGS. 3-5.Control of the switching device may be through an operator input or maybe controlled automatically by a microprocessor or controller of thecharging system.

What is claimed is:
 1. An apparatus for charging a first storage batteryand a second storage battery electrically connected together in series,comprising: a first positive electrical connector to electrically coupleto a positive terminal of the first storage battery and carry anelectrical signal; a second positive electrical connector toelectrically couple to the positive terminal of the first storagebattery and carry an electrical signal, the first and second positiveelectrical connectors forming a first Kelvin connection; a firstnegative electrical connector to electrically couple to a negativeterminal of the first storage battery and carry an electrical signal; asecond negative electrical connector to electrically couple to thenegative terminal of the first storage battery and carry an electricalsignal, the first and second negative electrical connectors forming asecond Kelvin connection; a third negative electrical connector toelectrically couple to a negative terminal of the second storage batteryand carry an electrical signal; a fourth negative electrical connectorto electrically couple to the negative terminal of the second storagebattery and carry an electrical signal, the third and fourth negativeelectrical connectors forming a third Kelvin connection; wherein atleast one of the positive electrical connectors and at least one of thenegative electrical connectors is configured to charge at least one ofthe first and second batteries; a charging source configured toselectively couple a charge signal to at least one of the first andsecond storage batteries through at least one of the positive electricalconnectors and one of the negative electrical connectors; measurementcircuitry configured to measure an electrical parameter of at least oneof the first and second storage batteries; a switching device configuredto selectively couple the charging source and the measurement circuitryto at least two of the first, second and third Kelvin connections; amicroprocessor configured to selectively control the switching device,charge the batteries, and measure a parameter of the batteries as afunction of the charging signal applied to the batteries.
 2. Theapparatus of claim 1 wherein the first positive and first negativeconnectors carry a voltage signal, the second positive and secondnegative connectors carry a current signal and the measured parameter isa function of the voltage and current signals.
 3. The apparatus of claim1 wherein the charging signal comprises an AC signal.
 4. The apparatusof claim 1 wherein the parameter is a dynamic parameter.
 5. Theapparatus of claim 4 wherein the dynamic parameter is a function ofstorage battery conductance.
 6. The apparatus of claim 1 wherein themicroprocessor provides an output related to storage battery conditionas a function of the measured parameter.
 7. The apparatus of claim 5wherein the output related to storage battery condition comprisesstorage battery cold cranking amps (CCA).
 8. The apparatus of claim 1including: voltage measurement circuitry coupled to the first positiveelectrical connector and first negative electrical connector toresponsively provide a measured voltage output related to a voltagebetween the first positive and first negative connectors; and themicroprocessor responsively provides the parameter as a function of themeasured voltage output.
 9. The apparatus of claim 1 including a memoryto store a rating related to a storage battery in a fully chargedcondition and wherein the microprocessor provides a state of chargeoutput as a function of the parameter output and the stored batteryrating.
 10. The apparatus of claim 1 wherein the parameter is a ratio ofa current through a storage battery and a voltage across a storagebattery.
 11. The apparatus of claim 1 wherein the charge signal from thecharging source is responsive to the measured parameter to therebycontrol charging of a storage battery.
 12. The apparatus of claim 1including input circuitry adapted to receive an input related to astorage battery.
 13. The apparatus of claim 12 wherein the inputcomprises a user input.
 14. The apparatus of claim 12 wherein the inputcomprises selected from the group of inputs consisting of storagebattery make, storage battery model, storage battery type, storagebattery part number and storage battery rating.
 15. The apparatus ofclaim 1 wherein the microprocessor determines state of charge of thestorage battery as a function of the parameter and the state of chargeincreases as storage battery impedance decreases.
 16. The apparatus ofclaim 1 wherein the charge signal includes a stepped DC component. 17.The apparatus of claim 1 wherein the microprocessor provides an outputindicative of a bad cell in the storage battery.
 18. The apparatus ofclaim 1 including a motor coupled to the switching device configured tochange a position of the switching device.
 19. The apparatus of claim 18wherein the motor is controlled by the microprocessor.
 20. The apparatusof claim 1 wherein the switching device is rotatable between positions.21. The apparatus of claim 1 wherein the switching device providesKelvin connections.
 22. The apparatus of claim 1 wherein the switchingdevice is movable between two positions.
 23. The apparatus of claim 1including a third positive electrical connector configured to couple toa positive terminal of the second battery and carry an electricalsignal, a fourth positive electrical connection configured to couple tothe positive terminal of the second battery and carry an electricalsignal, the third and fourth positive electrical connectors forming afourth Kelvin connection and wherein the switching device is furtherconfigured to selectively couple the charging source and the measurementcircuitry to the fourth Kelvin connection.
 24. The apparatus of claim 1wherein the second Kelvin connection is physically coupled to thenegative terminal of the first storage battery.
 25. The apparatus ofclaim 1 wherein the second Kelvin connection is physically coupled to apositive terminal of the second storage battery.